Ammonia, anhydrous

Endpoint summary

Additional information

Atmospheric ammonia reacts with ozone, hydroxyl radical, and atomic oxygen. In the aqueous environment, ammonia will be present as ammonia (NH3) or ammonium ion (NH4+); the relative proportions of the two chemical species are dependent on pH and (to a lesser extent) temperature. At environmentally relevant pH values of 5- 8, the predominant form will be NH4+. At higher pH values the proportion of ammonia (NH3) increases. Ammonia is environmentally ubiquitous as a consequence of natural degradation processes and animal excretion and has a critical role in the nitrogen cycle. When introduced into the aquatic environment, ammonia is rapidly converted into other nitrogenous forms under aerobic conditions. The major processes include fixation, assimilation, ammonification, nitrification and denitrification. Under aerobic conditions, ammonia in water is rapidly converted into nitrate by nitrification. Bacteria of the genus Nitrosomonas oxidise ammonia to nitrite, and Nitrobacter convert the nitrite into nitrate. The pH in water is increased by the presence of ammonia ions, in the form of hydroxide ions. Temperature, oxygen supply and pH of the water are factors in determining the rate of oxidation. Aerobic biological treatment (as utilised in wastewater treatment works) completely nitrifies ammonia to nitrate. Ammonia is assimilated by aquatic algae and macrophytes for use as a nitrogen source.